Use and Misuse of Opioids in Chronic Pain

Tramadol and Codeine Stacking/Boosting Dose Exposure Induced Neurotoxic Behaviors, Oxidative Stress, Mitochondrial Dysfunction, and Neurotoxic Genes in Adolescent Mice

In spite of the increasing epidemic of pharmaceutical opioids (codeine and tramadol) misuse and abuse among the adolescents, little is known about the neurotoxic consequences of the widespread practice of tramadol and codeine abuse involving increasing multiple doses across days, referred to as stacking and boosting. Hence, in this study, we replicated stacking and boosting doses of tramadol, codeine alone, or in combination on spontaneous motor activity and cognitive function in adolescent mice and adduced a plausible mechanism of possible neurotoxicity. Ninety-six adolescent mice were randomly distributed into 4 groups (n = 24 per group) and treated thrice daily for 9 days with vehicle, tramadol (20, 40, or 80 mg/kg), codeine (40, 80, or 160 mg/kg), or their combinations. Exposure of mice to tramadol induced hyperactivity and stereotypic behavior while codeine exposure caused hypoactivity and nootropic effect but tramadol-codeine cocktail led to marked reduction in spontaneous motor activity and cognitive function. In addition, tramadol, codeine, and their cocktail caused marked induction of nitroso-oxidative stress and inhibition of mitochondrial complex I activity in the prefrontal cortex (PFC) and midbrain (MB). Real-time PCR expression profiling of genes encoding neurotoxicity (RT) showed that tramadol exposure upregulate 57 and downregulate 16 neurotoxic genes, codeine upregulate 45 and downregulate 25 neurotoxic genes while tramadol-codeine cocktail upregulate 52 and downregulate 20 neurotoxic genes in the PFC. Findings from this study demonstrate that the exposure of adolescents mice to multiple and increasing doses of tramadol, codeine, or their cocktail lead to spontaneous motor coordination deficits indicative of neurotoxicity through induction of oxidative stress, inhibition of mitochondrial complex I activity and upregulation of neurotoxicity encoding genes in mice.

The epidemiology of multimorbidity in France: Variations by gender, age and socioeconomic factors, and implications for surveillance and prevention

Background

Robust public health and health system response to the increasing burden of multimorbidity worldwide requires detailed epidemiological examination of its key sociodemographic and geographic determinants. We investigated the role of gender, age and socioeconomic and geographic factors on multimorbidity (i.e., having two or more conditions) in the adult population in France and examined implications for surveillance and prevention.

Methods

We used data from two large nationwide representative surveys with cross-sectional and longitudinal health and socio-demographic indicators, conducted in France between 2008 and 2014. Morbidity counts and frequent dyads/triads of conditions independently impacting mortality, activity limitations, and perceived health were investigated with regard to differences in gender, age, socioeconomic (education, occupation and income) and geography (size of the urban unit and region).

Results

The component conditions of multimorbidity varied with gender and age. Women experienced multimorbidity 23–31% more frequently and at a younger age (5–15 years earlier) than men. Multimorbidity increased with age while its associations with most health indicators weakened with it. Multimorbidity was strongly and independently associated with socioeconomic indicators, with a strong inverse dose-response relationship with education, but less consistently with geographic factors.

Conclusions

Multimorbidity has diverse and variable components and impacts across gender and age. It is strongly associated with socioeconomic factors, notably educational level, for which causality appears likely. Consideration of this diversity and variability, its common occurrence in dyads and triads, and its impact on health outcomes according to age and gender may contribute to efficient surveillance and support the identification of prevention strategies targeting middle-aged men and women.

Hyperbaric Oxygen Therapy for Pain, Opioid Withdrawal, and Related Symptoms: A Pilot Randomized Controlled Trial

BACKGROUND

Pain, drug cravings, and opioid withdrawal symptoms can interfere with substance use disorder or opioid tapering treatment goals.

AIM

This pilot study investigated the feasibility of a protocol designed to test opioid withdrawal symptom relief relative to a sham condition after two consecutive days of hyperbaric oxygen therapy (HBOT) for adults prescribed daily methadone for opioid use disorder.

METHOD

Using a double-blind protocol, eight adults were randomized to receive either a full 90-minute HBOT dose in a pressurized chamber with 100% oxygen at 2.0 atmospheres absolute (ATA) or a sham condition receiving 21% oxygen (equivalent to room air within the chamber) at a minimal pressure of ≤1.3 ATA. Measures included study retention, treatment satisfaction, and pre- and post-intervention effects for opioid withdrawal symptoms, drug cravings, pain intensity and interference, sleep quality, and mood.

RESULTS

Study retention and treatment satisfaction was high. All measurements improved more, on average, for participants receiving full-dose HBOT treatment than among participants receiving sham treatments except for clinically observed withdrawal symptoms. The largest positive effects were observed in measurements of pain intensity and drug craving.

CONCLUSIONS

These pilot results provide evidence to support a fully powered study of HBOT as a potential treatment adjunct for adults receiving methadone for opioid use disorder. Trends towards symptom improvements were detected from pre- to post-HBOT in the full treatment arm versus sham condition. More research into novel non-pharmacologic options to relieve distressing symptoms related to pain and opioid use disorder is essential to improve clinical outcomes.

Associations of opioid prescription dose and discontinuation with risk of substance-related morbidity in long-term opioid therapy

ABSTRACT

Efforts to reduce opioid-related harms have decreased opioid prescription but have provoked concerns about unintended consequences, particularly for long-term opioid therapy (LtOT) recipients. Research is needed to address the knowledge gap regarding how risk of substance-related morbidity changes across LtOT and its discontinuation. This study used nationwide commercial insurance claims data and a within-individual design to examine associations of LtOT dose and discontinuation with substance-related morbidity. We identified 194,839 adolescents and adults who initiated opioid prescription in 2010 to 2018 and subsequently received LtOT. The cohort was followed for a median of 965 days (interquartile range, 525-1550), of which a median of 176 days (119-332) were covered by opioid prescription. During follow-up, there were 17,582 acute substance-related morbidity events, defined as claims for emergency visits, inpatient hospitalizations, and ambulance transportation with substance use disorder or overdose diagnoses. Relative to initial treatment, risk was greater within individual during subsequent periods of >60 to 120 (adjusted odds ratio [OR], 1.29; 95% CI, 1.12 to 1.49) and >120 (OR, 1.48; 95% CI, 1.24-1.76) daily morphine milligram equivalents. Risk was also greater during days 1 to 30 after discontinuations than during initial treatment (OR, 1.19; 95% CI, 1.05-1.35). However, it was no greater than during the 30 days before discontinuations, indicating that the risk may not be wholly attributable to discontinuation itself. Results were supported by a negative control pharmacotherapy analysis and additional sensitivity analyses. They suggest that LtOT recipients may experience increased substance-related morbidity risk during treatment subsequent to initial opioid prescription, particularly in periods involving higher doses.

The Impact of Multidisciplinary Conferences on Healthcare Utilization in Chronic Pain Patients

Approximately 100 million adults in the United States have chronic pain, though only a subset utilizes the vast majority of healthcare resources. Multidisciplinary care has been shown to improve outcomes in a variety of clinical conditions. There is concern that multidisciplinary care of chronic pain patients may overwhelm existing resources and increase healthcare utilization due to the volume of patients and the complexity of care. We report our findings on the use of multidisciplinary conferences (MDC) to facilitate care for the most complex patients seen at our tertiary center. Thirty-two of nearly 2,000 patients seen per year were discussed at the MDC, making up the top 2% of complex patients in our practice. We evaluated patients' numeric rating score (NRS) of pain, medication use, hospitalizations, emergency department visits, and visits to pain specialists prior to their enrollment in MDC and 1 year later. Matched samples were compared using Wilcoxon's signed rank test. Patients' NRS scores significantly decreased from 7.64 to 5.54 after inclusion in MDC (p < 0.001). A significant decrease in clinic visits (p < 0.001) and healthcare utilization (p < 0.05) was also observed. Opioid and non-opioid prescriptions did not change significantly (p = 0.43). 83% of providers agreed that MDC improved patient care. While previous studies have shown the effect of multi-disciplinary care, we show notable improvements with a team established around a once-a-month MDC.

Analysis of Antidepressant, Benzodiazepine Anxiolytic, and Hypnotic Use When Treating Depression, Anxiety, and Aggression in Pain Clinic Patients Treated for Neuropathic Pain

Depression, anxiety, and aggression accompany neuropathic pain. Effective treatment of these comorbidities enhances the outcomes of pain management. Therefore, the study was designed to analyze the relationship between the intensity of depression, anxiety, and aggression and the pharmacotherapy applied in the daily practice of treating neuropathic pain. The aim of the study was to evaluate the frequency of using antidepressants (ADs), benzodiazepine anxiolytics (BDAs), and hypnotics, and the influence of administering these on the intensity of depression, anxiety, and aggression in patients diagnosed with neuropathic pain. A multi-center survey was conducted among 421 patients. An evaluation of the severity of depression, anxiety, and aggression was made using the Hospital Anxiety and Depression Scale—Modified Version (HADS-M). Among the patients treated due to neuropathic pain, ADs are used much more often than BDAs and hypnotics. Depression was well controlled, while anxiety was identified as a possible uncontrolled therapeutic problem in these patients, despite the correlation between the frequency of AD and hypnotics usage and the severity of anxiety. We also found that women show a higher level of intensity in both anxiety and depression, but this does not influence the frequency of their being administered ADs, BDAs, and hypnotics.

Initiation of Opioid Prescription and Risk of Suicidal Behavior Among Youth and Young Adults

BACKGROUND AND OBJECTIVES

Opioids are involved in an increasing proportion of suicide deaths. This study examined the association between opioid analgesic prescription initiation and suicidal behavior among young people.

METHODS

We analyzed Swedish population-register data on 1 895 984 individuals ages 9 to 29 years without prior recorded opioid prescriptions. We identified prescriptions dispensed from January 2007 onward and diagnosed self-injurious behavior and death by suicide through December 2013. We first compared initiators with demographically matched noninitiators. To account for confounding, we applied an active comparator design, which examined suicidal behavior among opioid initiators relative to prescription nonsteroidal antiinflammatory drug (NSAID) initiators while inverse-probability-of-treatment weighting with individual and familial covariates.

RESULTS

Among the cohort, 201 433 individuals initiated opioid prescription. Relative to demographically matched noninitiators, initiators (N = 180 808) had more than doubled risk of incident suicidal behavior (hazard ratio = 2.64; 95% confidence interval [CI], 2.47-2.81). However, in the active comparator design, opioid initiators (N = 86 635) had only 19% relatively greater risk of suicidal behavior compared with NSAID initiators (N = 255 096; hazard ratio = 1.19; 95% CI,: 1.11-1.28), corresponding to a weighted 5-year cumulative incidence of 2.2% (95% CI, 2.1-2.4) for opioid and 1.9% (95% CI, 1.9-2.0) for NSAID initiators. Most sensitivity analyses produced comparable results.

CONCLUSIONS

Opioid initiation may make only a small contribution to the elevated risk of suicidal behavior among young people receiving pharmacologic pain management. In weighing benefits and harms of opioid initiation, our results suggest that increased risk of suicidal behavior may not be a major concern.

Ketorolac Administration After Colorectal Surgery Increases Anastomotic Leak Rate: A Meta-Analysis and Systematic Review

Objective

This meta-analysis aimed to evaluate whether ketorolac administration is associated with an increased anastomotic leak rate after colorectal surgery.

Methods

The literature was searched using the Web of Science, Embase, and PubMed databases, and the search ended on May 31, 2020. The Newcastle–Ottawa Scale was used to assess methodological quality. Statistical heterogeneity was assessed using the Chi-square Q test and I² statistics. Subgroup analysis was performed, and Egger's test was used to assess publication bias.

Results

This meta-analysis included seven studies with 400,822 patients. Our results demonstrated that ketorolac administration after surgery increases the risk of anastomotic leak [OR = 1.41, 95% CI: 0.81–2.49, Z = 1.21, P = 0.23]. Low heterogeneity was observed across these studies (I² = 0%, P = 0.51). The results of subgroup analysis showed that the use of ketorolac in case–control and retrospective cohort studies significantly increased the risk of anastomotic leak (P < 0.05). Furthermore, the subgroup analysis revealed that ketorolac use increased anastomotic leak rate in patients in the United States and Canada, and ketorolac plus morphine use did not increase anastomotic leak rate in Taiwanese patients (P < 0.05). No significant publication bias was observed (P = 0.126). Moreover, the analysis of risk factors related to anastomotic leak rate indicated that the total use of ketorolac did not increase the risk of anastomotic leak similar to the control group (P > 0.05).

Conclusion

The meta-analysis indicates that the use of ketorolac increases the risk of anastomotic leak after colorectal surgery.

Systematic Review Registration

PROSPERO, identifier CRD42020195724.

An overview of the use and misuse/abuse of opioid analgesics in different world regions and future perspectives

Opioids are an important therapeutic option for severe resistant chronic pain but, in the absence of proper oversight, their use has risks. The level of prescription opioid misuse/abuse differs among countries, due to differences in healthcare systems and pain management approaches. However, evaluating the true dimension of prescription opioid misuse/abuse is complicated by statistical reporting which often does not differentiate between prescription and illicit opioid use, or between prescription opioid use by patients and nonpatients, highlighting a need for greater uniformity. Parallel efforts to educate patients and the general public about opioid risks, facilitate appropriate analgesic prescribing and identify alternative formulations or options to use instead of or with opioids, may contribute to optimizing prescription opioid use for pain management.

Are x-waiver trainings enough? Facilitators and barriers to buprenorphine prescribing after x-waiver trainings

BACKGROUND

In the United States, an x-waiver credential is necessary to prescribe buprenorphine medication treatment for opioid use disorder (B-MOUD). Historically, this process has required certified training, which could be a barrier to obtaining an x-waiver and subsequently prescribing. To address this barrier, the US recently removed the training requirement for some clinicians. We sought to determine if clinicians who attended x-waiver training went on to obtain an x-waiver and prescribe B-MOUD, and to examine what facilitated or impeded B-MOUD prescribing.

METHODS

In September 2020, we conducted a cross-sectional, electronic survey of attendees of 15 in-person x-waiver pieces of training from June 2018 to January 2020 within the Veterans Health Administration (VHA). Of the attendees (n = 321), we surveyed current VHA clinicians who recalled taking the training. The survey assessed whether clinicians obtained the x-waiver, had prescribed B-MOUD, and barriers or facilitators that influenced B-MOUD prescribing.

RESULTS

Of 251 eligible participants, 62 (24.7%) responded to the survey, including 27 (43.5%) physicians, 16 (25.8%) advanced practice clinicians, and 12 (19.4%) pharmacists. Of the 43 clinicians who could prescribe, 29 (67.4%) had obtained their x-waiver and 16 (37.2%) had reported prescribing B-MOUD. Prominent barriers to prescribing B-MOUD included a lack of supporting clinical staff and competing demands on time. The primary facilitator to prescribing was leadership support.

CONCLUSIONS

Nine months after x-waiver training, two-thirds of clinicians with prescribing credentials had obtained their x-waiver and one-third were prescribing B-MOUD. Removing the x-waiver training may not have the intended policy effect as other barriers to B-MOUD prescribing persist.

Pramipexole treatment attenuates mechanical hypersensitivity in male rats experiencing chronic inflammatory pain

Opioids are commonly prescribed for pain despite growing evidence of their low efficacy in the treatment of chronic inflammatory pain and the high potential for misuse. There is a clear need to investigate non-opioid alternatives for the treatment of pain. In the present study, we tested the hypothesis that acute and repeated dopamine agonist treatment would attenuate mechanical hypersensitivity in male Long-Evans rats experiencing chronic inflammatory pain. We used two clinically available therapeutics, l-DOPA (precursor of dopamine biosynthesis) and pramipexole (dopamine D2/3 receptor agonist), to examine the functional role of dopamine signaling on mechanical hypersensitivity using an animal model of chronic inflammatory pain (complete Freund's adjuvant, CFA). We found that both acute and repeated pramipexole treatment attenuated hyperalgesia-like behavior in CFA-treated animals but exhibited no analgesic effects in control animals. In contrast, there was no effect of acute or repeated l-DOPA treatment on mechanical hypersensitivity in either CFA- or saline-treated animals. Notably, we discovered some extended effects of l-DOPA and pramipexole on decreasing pain-like behavior at three days and one week post-drug treatment. We also examined the effects of pramipexole treatment on glutamatergic and presynaptic signaling in pain- and reward-related brain regions including the nucleus accumbens (NAc), dorsal striatum (DS), ventral tegmental area (VTA), cingulate cortex (CC), central amygdala (CeA), and periaqueductal gray (PAG). We found that pramipexole treatment decreased AMPA receptor phosphorylation (pGluR1845) in the NAc and DS but increased pGluR1845 in the CC and CeA. A marker of presynaptic vesicle release, pSynapsin, was also increased in the DS, VTA, CC, CeA, and PAG following pramipexole treatment. Interestingly, pramipexole increased pSynapsin in the NAc of saline-treated animals, but not CFA-treated animals, suggesting blunted presynaptic vesicle release in the NAc of CFA-treated animals following pramipexole treatment. To examine the functional implications of impaired presynaptic signaling in the NAc of CFA animals, we used ex vivo electrophysiology to examine the effects of pramipexole treatment on the intrinsic excitability of NAc neurons in CFA- and saline-treated animals. We found that pramipexole treatment reduced NAc intrinsic excitability in saline-treated animals but produced no change in NAc intrinsic excitability in CFA-treated animals. These findings indicate alterations in dopamine D2/3 receptor signaling in the NAc of animals with a history of chronic pain in association with the anti-hyperalgesic effects of pramipexole treatment.

Barriers and enablers to monitoring and deprescribing opioid analgesics for chronic non-cancer pain: a systematic review with qualitative evidence synthesis using the Theoretical Domains Framework

Background

Understanding barriers and enablers to monitoring and deprescribing opioids will enable the development of tailored interventions to improve both practices.

Objective

To perform a qualitative evidence synthesis of the barriers and enablers to monitoring ongoing appropriateness and deprescribing of opioids for chronic non-cancer pain (CNCP) and to map the findings to the Theoretical Domains Framework (TDF).

Methods

We included English-language qualitative studies that explored healthcare professional (HCP), patient, carer and the general public’s perceptions regarding monitoring and deprescribing opioids for CNCP. We searched MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Allied and Complementary Medicine Database (AMED) and PsycINFO from inception to August 2020. Two authors independently selected the studies, extracted the data, assessed the methodological quality using the Critical Appraisal Skills Programme, and assessed the confidence in the findings using GRADE CERQual (Grading of Recommendations Assessment, Development, and Evaluation Confidence in the Evidence from Reviews of Qualitative Research). We used an inductive approach to synthesis of qualitative data and mapped identified themes to TDF domains.

Results

From 6948 records identified we included 21 studies, involving 209 HCPs and 330 patients. No studies involved carers or the general public. Five barrier themes were identified: limited alternatives to opioids, management of pain is top priority, patient understanding, expectations and experiences, prescriber pressures, and reluctance to change. Four enabler themes were identified: negative effects of opioids and benefits of deprescribing, clear communication and expectations for deprescribing, support for patients, and support for prescribers. 16 barrier and 12 enabler subthemes were identified; most were graded as high (n=15) or moderate (n=9) confidence. The TDF domains ‘beliefs about consequences’, ‘environmental context and resources’, ‘social influences’ and ‘emotion’ were salient for patients and HCPs. The domains ‘skills’ and ‘beliefs about capabilities’ were more salient for HCPs.

Conclusion

Future implementation interventions aimed at monitoring and deprescribing opioids should target the patient and HCP barriers and enablers identified in this synthesis.

PROSPERO registration number

CRD42019140784.

Analgesic Opioid Ligand Discovery Based on Nonmorphinan Scaffolds Derived from Natural Sources

Strong opioid analgesics, including morphine, are the mainstays for treating moderate to severe acute pain and alleviating chronic cancer pain. However, opioid-related adverse effects, including nausea or vomiting, sedation, respiratory depression, constipation, pruritus (itch), analgesic tolerance, and addiction and abuse liability, are problematic. In addition, the use of opioids to relieve chronic noncancer pain is controversial due to the "opioid crisis" characterized by opioid misuse or abuse and escalating unintentional death rates due to respiratory depression. Hence, considerable research internationally has been aimed at the "Holy Grail" of the opioid analgesic field, namely the discovery of novel and safer opioid analgesics with improved opioid-related adverse effects. In this Perspective, medicinal chemistry strategies are addressed, where structurally diverse nonmorphinan-based opioid ligands derived from natural sources were deployed as lead molecules. The current state of play, clinical or experimental status, and novel opioid ligand discovery approaches are elaborated in the context of retaining analgesia with improved safety and reduced adverse effects, especially addiction liability.

Examination of the Novel Sigma-1 Receptor Antagonist, SI 1/28, for Antinociceptive and Anti-allodynic Efficacy against Multiple Types of Nociception with Fewer Liabilities of Use

Neuropathic pain is a significant problem with few effective treatments lacking adverse effects. The sigma-1 receptor (S1R) is a potential therapeutic target for neuropathic pain, as antagonists for this receptor effectively ameliorate pain in both preclinical and clinical studies. The current research examines the antinociceptive and anti-allodynic efficacy of SI 1/28, a recently reported benzylpiperazine derivative and analog of the S1R antagonist SI 1/13, that was 423-fold more selective for S1R over the sigma-2 receptor (S2R). In addition, possible liabilities of respiration, sedation, and drug reinforcement caused by SI 1/28 have been evaluated. Inflammatory and chemical nociception, chronic nerve constriction injury (CCI) induced mechanical allodynia, and adverse effects of sedation in a rotarod assay, conditioned place preference (CPP), and changes in breath rate and locomotor activity were assessed after i.p. administration of SI 1/28. Pretreatment with SI 1/28 produced dose-dependent antinociception in the formalin test, with an ED50 (and 95% C.I.) value of 13.2 (7.42-28.3) mg/kg, i.p. Likewise, SI 1/28 produced dose-dependent antinociception against visceral nociception and anti-allodynia against CCI-induced neuropathic pain. SI 1/28 demonstrated no impairment of locomotor activity, conditioned place preference, or respiratory depression. In summary, SI 1/28 proved efficacious in the treatment of acute inflammatory pain and chronic neuropathy without liabilities at therapeutic doses, supporting the development of S1R antagonists as therapeutics for chronic pain.

Physician Liability for Suicide after Negligent Tapering of Opioids

The precipitous and medically contraindicated reduction or "tapering" of opioids for patients with chronic pain due to serious medical conditions has caused needless suffering and, increasingly, suicide. Physicians could be liable for wrongful death based on negligent tapering of opioids.

α1-Antitrypsin derived SP16 peptide demonstrates efficacy in rodent models of acute and neuropathic pain

SP16 is an innovative peptide derived from the carboxyl-terminus of α1-Antitrypsin (AAT), corresponding to residues 364-380, and contains recognition sequences for the low-density lipoprotein receptor-related protein-1 (LRP1). LRP1 is an endocytic and cell-signaling receptor that regulates inflammation. Deletion of Lrp1 in Schwann cells increases neuropathic pain; however, the role of LRP1 activation in nociceptive and neuropathic pain regulation remains unknown. Herein, we show that SP16 is bioactive in sensory neurons in vitro. Neurite length and regenerative gene expression were increased by SP16. In PC12 cells, SP16 activated Akt and ERK1/2 cell-signaling in an LRP1-dependent manner. When formalin was injected into mouse hind paws, to model inflammatory pain, SP16 dose-dependently attenuated nociceptive pain behaviors in the early and late phases. In a second model of acute pain using capsaicin, SP16 significantly reduced paw licking in both male and female mice (p < .01) similarly to enzymatically inactive tissue plasminogen activator, a known LRP1 interactor. SP16 also prevented development of tactile allodynia after partial nerve ligation and this response was sustained for nine days (p < .01). Immunoblot analysis of the injured nerve revealed decreased CD11b (p < .01) and Toll-like receptor-4 (p < .005). In injured dorsal root ganglia SP16 reduced CD11b⁺ cells (p < .05) and GFAP (p < .005), indicating that inflammatory cell recruitment and satellite cell activation were inhibited. In conclusion, administration of SP16 blocked pain-related responses in three distinct pain models, suggesting efficacy against acute nociceptive, inflammatory, and neuropathic pain. SP16 also attenuated innate immunity in the PNS. These studies identify SP16 as a potentially effective treatment for pain.

Pain-driven emergency department visits and food insecurity: a cross-sectional study linking Canadian survey and health administrative data

BACKGROUND

As the leading cause of emergency department visits in Canada, pain disproportionately affects socioeconomically disadvantaged populations. We examine the association between household food insecurity and individuals' pain-driven emergency department visits.

METHODS

We designed a cross-sectional study linking the Canadian Community Health Survey 2005-2017 to the National Ambulatory Care Reporting System 2003-2017. Food insecurity was measured using a validated questionnaire. We excluded individuals with missing food insecurity status, individuals younger than 12 years and jurisdiction-years with partial emergency department records. We assessed emergency department visits driven by pain at different sites (migraine, other headaches, chest-throat pain, abdomen-pelvis pain, dorsalgia, joint pain, limb pain, other pain) and their characteristics (frequency, cause, acuity and time of emergency department visit) in Ontario and Alberta. We adjusted for sociodemographic characteristics, lifestyle and prior non-pain-driven emergency department visits in the models.

RESULTS

The sample contained 212 300 individuals aged 12 years and older. Compared with food-secure individuals, marginally, moderately and severely food-insecure people had 1.42 (95% confidence interval [CI] 1.20-1.68), 1.64 (95% CI 1.37-1.96) and 1.99 (95% CI 1.61-2.46) times higher adjusted incidence rates of pain-driven emergency department visits, respectively. The association was similar across sexes and significant among adults but not adolescents. Food insecurity was further associated with site-specific pain, with severely food-insecure individuals having significantly higher pain incidence than food-secure individuals. Severe food insecurity predicted more frequent, multicause, high-acuity and after-hours emergency department visits.

INTERPRETATION

Household food insecurity status is significantly associated with pain-driven emergency department visits in the Canadian population. Policies targeting food insecurity may reduce pain and emergency department utilization.

Development of ProTx-II Analogues as Highly Selective Peptide Blockers of Nav1.7 for the Treatment of Pain

Inhibitor cystine knot peptides, derived from venom, have evolved to block ion channel function but are often toxic when dosed at pharmacologically relevant levels in vivo. The article describes the design of analogues of ProTx-II that safely display systemic in vivo blocking of Na_v1.7, resulting in a latency of response to thermal stimuli in rodents. The new designs achieve a better in vivo profile by improving ion channel selectivity and limiting the ability of the peptides to cause mast cell degranulation. The design rationale, structural modeling, in vitro profiles, and rat tail flick outcomes are disclosed and discussed.

Pain Reduction in Adults with Limb Spasticity Following Treatment with IncobotulinumtoxinA: A Pooled Analysis

Some studies have shown that incobotulinumtoxinA reduces spasticity-associated pain, but further evidence is needed. This exploratory analysis pooled pain-relief data from six Phase 2 or 3 studies of incobotulinumtoxinA (four placebo-controlled studies) for treating upper limb spasticity in adults. Spasticity-associated pain was assessed at baseline and 4 weeks post incobotulinumtoxinA injection using the disability assessment scale (DAS) for pain. Only data for patients with pain at baseline were analysed. Overall, 544 (incobotulinumtoxinA, N = 415; placebo, N = 129) of 937 patients (58.1%) experienced pain at baseline. At Week 4, a significantly greater proportion of incobotulinumtoxinA- (52.1%) than placebo-treated patients (28.7%; Chi-square p < 0.0001) showed a response (≥1-point improvement in DAS pain score). In logistic regression analysis, incobotulinumtoxinA-treated patients were 2.6 times more likely to achieve this endpoint than placebo-treated patients. A significant difference between incobotulinumtoxinA and placebo was observed regardless of baseline pain severity. Additionally, 27.1% of incobotulinumtoxinA- versus 12.4% of placebo-treated patients reported complete pain relief at Week 4 (p = 0.0006). Pain relief increased with multiple injection cycles. To achieve patient-centred care, pain relief may be considered a treatment goal in adults with spasticity-associated pain regardless of pain severity. This study contributes to understanding the benefits of incobotulinumtoxinA in treating limb spasticity-associated pain.

Conolidine: A Novel Plant Extract for Chronic Pain

Pain, the most common symptom reported among patients in the primary care setting, is complex to manage. Opioids are among the most potent analgesics agents for managing pain. Since the mid-1990s, the number of opioid prescriptions for the management of chronic non-cancer pain (CNCP) has increased by more than 400%, and this increased availability has significantly contributed to opioid diversion, overdose, tolerance, dependence, and addiction. Despite the questionable effectiveness of opioids in managing CNCP and their high rates of side effects, the absence of available alternative medications and their clinical limitations and slower onset of action has led to an overreliance on opioids. Conolidine is an indole alkaloid derived from the bark of the tropical flowering shrub Tabernaemontana divaricate used in traditional Chinese, Ayurvedic, and Thai medicine. Conolidine could represent the beginning of a new era of chronic pain management. It is now being investigated for its effects on the atypical chemokine receptor (ACK3). In a rat model, it was found that a competitor molecule binding to ACKR3 resulted in inhibition of ACKR3's inhibitory activity, causing an overall increase in opiate receptor activity. Although the identification of conolidine as a potential novel analgesic agent provides an additional avenue to address the opioid crisis and manage CNCP, further studies are necessary to understand its mechanism of action and utility and efficacy in managing CNCP.

Alcohol-medication interactions: A systematic review and meta-analysis of placebo-controlled trials

Alcohol and other xenobiotics may limit the therapeutic effects of medications. We aimed at investigating alcohol-medication interactions (AMI) after the exclusion of confounding effects related to other xenobiotics. We performed a systematic review and meta-analysis of controlled studies comparing the effects induced by alcohol versus placebo on pharmacodynamic and/or pharmacokinetic parameters of approved medications. Certainty in the evidence of AMI was assessed when at least 3 independent studies and at least 200 participants were available. We included 107 articles (3097 participants): for diazepam, cannabis, opioids, and methylphenidate, we found significant AMI and enough data to assign the certainty of evidence. Alcohol consumption significantly increases the peak plasma concentration of diazepam (low certainty; almost 290 participants), cannabis (high certainty; almost 650 participants), opioids (low certainty; 560 participants), and methylphenidate (moderate certainty; 290 participants). For most medications, we found some AMI but not enough data to assign them the certainty grades; for some medications, we found no differences between alcohol and placebo in any outcomes evaluated. Our results add further evidence for interactions between alcohol and certain medications after the exclusion of confounding effects related to other xenobiotics. Physicians should advise patients who use these specific medications to avoid alcohol consumption. Further studies with appropriate control groups, enough female participants to investigate sex differences, and elderly population are needed to expand our knowledge in this field. Short phrases suitable for indexing terms.

Bifunctional μ opioid and σ1 receptor ligands as novel analgesics with reduced side effects

Opioid analgesics are highly effective painkillers for the treatment of moderate or severe pain, but they are associated with a number of undesirable adverse effects, including the development of tolerance, addiction, constipation and life-threatening respiratory depression. The development of new and safer analgesics with innovative mechanisms of action, which can enhance the efficacy in comparison to available treatments and reduce their side effects, is urgently needed. The sigma-1 receptor (σ1R), a unique Ca2+-sensing chaperone protein, is expressed throughout pain-modulating tissues and affects neurotransmission by interacting with different protein partners, including molecular targets that participate in nociceptive signalling, such as the μ-opioid receptor (MOR), N-methyl-d-aspartate receptor (NMDAR) and cannabinoid 1 receptor (CB1R). Overwhelming pharmacological and genetic evidence indicates that σ1R antagonists induce anti-hypersensitive effects in sensitising pain conditions (e.g. chemically induced, inflammatory and neuropathic pain) and enhance opioid analgesia but not opioid-mediated detrimental effects. It has been suggested that balanced modulation of MORs and σ1Rs may improve both the therapeutic efficacy and safety of opioids. This review summarises the functional profiles of ligands with mixed MOR agonist and σ1R antagonist activities and highlights their therapeutic potentials for pain management. Dual MOR agonism/σ1R antagonism represents a promising avenue for the development of potent and safer analgesics.

A social affective neuroscience lens on placebo analgesia

Pain is a fundamental experience that promotes survival. In humans, pain stands at the intersection of multiple health crises: chronic pain, the opioid epidemic, and health disparities. The study of placebo analgesia highlights how social, cognitive, and affective processes can directly shape pain, and identifies potential paths for mitigating these crises. This review examines recent progress in the study of placebo analgesia through affective science. It focuses on how placebo effects are shaped by expectations, affect, and the social context surrounding treatment, and discusses neurobiological mechanisms of placebo, highlighting unanswered questions and implications for health. Collaborations between clinicians and social and affective scientists can address outstanding questions and leverage placebo to reduce pain and improve human health.

Improving the Delivery of Chronic Opioid Therapy Among People Living With Human Immunodeficiency Virus: A Cluster Randomized Clinical Trial

BACKGROUND

Chronic pain is prevalent among people living with human immunodeficiency virus (PLWH); managing pain with chronic opioid therapy (COT) is common. Human immunodeficiency virus (HIV) providers often diverge from prescribing guidelines.

METHODS

This 2-arm, unblinded, cluster-randomized clinical trial assessed whether the Targeting Effective Analgesia in Clinics for HIV (TEACH) intervention improves guideline-concordant care compared to usual care for PLWH on COT. The trial was implemented from 2015 to 2018 with 12-month follow-up at safety-net hospital-based HIV clinics in Boston and Atlanta. We enrolled 41 providers and their 187 patients on COT. Prescribers were randomized 1:1 to either a 12-month intervention consisting of a nurse care manager with an interactive electronic registry, opioid education, academic detailing, and access to addiction specialists or a control condition consisting of usual care. Two primary outcomes were assessed through electronic medical records: ≥2 urine drug tests and any early COT refills by 12 months. Other outcomes included possible adverse consequences.

RESULTS

At 12 months, the TEACH intervention arm had higher odds of ≥2 urine drug tests than the usual care arm (71% vs 20%; adjusted odds ratio [AOR], 13.38 [95% confidence interval {CI}, 5.85-30.60]; P < .0001). We did not detect a statistically significant difference in early refills (22% vs 30%; AOR, 0.55 [95% CI, .26-1.15]; P = .11), pain severity (6.30 vs 5.76; adjusted mean difference, 0.10 [95% CI, -1.56 to 1.75]; P = .91), or HIV viral load suppression (86.9% vs 82.1%; AOR, 1.21 [95% CI, .47-3.09]; P = .69).

CONCLUSIONS

TEACH is a promising intervention to improve adherence to COT guidelines without evident adverse consequences.

An endogenous opioid circuit determines state-dependent reward consumption

µ-Opioid peptide receptor (MOPR) stimulation alters respiration, analgesia and reward behaviour, and can induce substance abuse and overdose1-3. Despite its evident importance, the endogenous mechanisms for MOPR regulation of consummatory behaviour have remained unknown4. Here we report that endogenous MOPR regulation of reward consumption in mice acts through a specific dorsal raphe to nucleus accumbens projection. MOPR-mediated inhibition of raphe terminals is necessary and sufficient to determine consummatory response, while select enkephalin-containing nucleus accumbens ensembles are engaged prior to reward consumption, suggesting that local enkephalin release is the source of the endogenous MOPR ligand. Selective modulation of nucleus accumbens enkephalin neurons and CRISPR-Cas9-mediated disruption of enkephalin substantiate this finding. These results isolate a fundamental endogenous opioid circuit for state-dependent consumptive behaviour and suggest alternative mechanisms for opiate modulation of reward.

Recent Chemical and Pharmacological Developments on 14-Oxygenated-N-methylmorphinan-6-ones

Adequate pain management, particularly chronic pain, remains a major challenge associated with modern-day medicine. Current pharmacotherapy offers unsatisfactory long-term solutions due to serious side effects related to the chronic administration of analgesic drugs. Morphine and structurally related derivatives (e.g., oxycodone, oxymorphone, buprenorphine) are highly effective opioid analgesics, mediating their effects via the activation of opioid receptors, with the mu-opioid receptor subtype as the primary molecular target. However, they also cause addiction and overdose deaths, which has led to a global opioid crisis in the last decades. Therefore, research efforts are needed to overcome the limitations of present pain therapies with the aim to improve treatment efficacy and to reduce complications. This review presents recent chemical and pharmacological advances on 14-oxygenated-N-methylmorphinan-6-ones, in the search of safer pain therapeutics. We focus on drug design strategies and structure-activity relationships on specific modifications in positions 5, 6, 14 and 17 on the morphinan skeleton, with the goal of aiding the discovery of opioid analgesics with more favorable pharmacological properties, potent analgesia and fewer undesirable effects. Targeted molecular modifications on the morphinan scaffold can afford novel opioids as bi- or multifunctional ligands targeting multiple opioid receptors, as attractive alternatives to mu-opioid receptor selective analgesics.

GPR171 Agonist Reduces Chronic Neuropathic and Inflammatory Pain in Male, But Not Female Mice

Chronic pain is a growing public health crisis that requires exigent and efficacious therapeutics. GPR171 is a promising therapeutic target that is widely expressed through the brain, including within the descending pain modulatory regions. Here, we explore the therapeutic potential of the GPR171 agonist, MS15203, in its ability to alleviate chronic pain in male and female mice using a once-daily systemic dose (10 mg/kg, i.p.) of MS15203 over the course of 5 days. We found that in our models of Complete Freund's Adjuvant (CFA)-induced inflammatory pain and chemotherapy-induced peripheral neuropathy (CIPN), MS15203 did not alleviate thermal hypersensitivity and allodynia, respectively, in female mice. On the other hand, MS15203 treatment decreased the duration of thermal hypersensitivity in CFA-treated male mice following 3 days of once-daily administration. MS15203 treatment also produced an improvement in allodynia in male mice, but not female mice, in neuropathic pain after 5 days of treatment. Gene expression of GPR171 and that of its endogenous ligand BigLEN, encoded by the gene PCSK1N, were unaltered within the periaqueductal gray (PAG) in both male and female mice following inflammatory and neuropathic pain. However, following neuropathic pain in male mice, the protein levels of GPR171 were decreased in the PAG. Treatment with MS15203 then rescued the protein levels of GPR171 in the PAG of these mice. Taken together, our results identify GPR171 as a GPCR that displays sexual dimorphism in alleviation of chronic pain. Further, our results suggest that GPR171 and MS15203 have demonstrable therapeutic potential in the treatment of chronic pain.

The potential for diversion of prescribed opioids among orthopaedic patients: Results of an anonymous patient survey

INTRODUCTION

Diversion of prescription opioid medication is a contributor to the opioid epidemic. Safe handling practices can reduce the risk of diversion. We aimed to understand: 1) if orthopaedic patients received instructions on how to safely handle opioids, 2) their typical storage/disposal practices, and 3) their willingness to participate in an opioid disposal program (ODP).

METHODS

Cross-sectional study of adult orthopaedic patients who completed an anonymous survey on current or past prescription opioid use, instruction on handling, storage and disposal practices, presence of children in the household, and willingness to participate in an ODP. Frequencies and percentages of responses were computed, both overall and stratified by possession of unused opioids.

RESULTS

569 respondents who reported either current or past prescription opioid use were analyzed. 44% reported receiving storage instructions and 56% reported receiving disposal instructions from a health care provider. Many respondents indicated unsafe handling practices: possessing unused opioids (34%), using unsafe storage methods (90%), and using unsafe disposal methods (34%). Respondents with unused opioids were less likely to report receiving handling instructions or using safe handling methods, and 47% of this group reported having minors or young adults in the household. Respondents who received storage and disposal instructions were more likely to report safe storage and disposal methods. Seventy-four percent of respondents reported that they would participate in an ODP.

CONCLUSION

While many orthopaedic patients report inadequate education on safe opioid handling and using unsafe handling practices, findings suggest targeted education is associated with better behaviours. However, patients are willing to safely dispose of unused medication if provided a convenient option. These findings suggest a need to address patient knowledge and behavior regarding opioid handling to reduce the risk of opioid diversion.

In vivo and in vitro Characterization of a Partial Mu Opioid Receptor Agonist, NKTR-181, Supports Future Therapeutic Development

Mu opioid receptor (MOPr) agonists are well-known and frequently used clinical analgesics but are also rewarding due to their highly addictive and often abusive properties. This may lead to opioid use disorder (OUD) a disorder that effects millions of people worldwide. Therefore, novel compounds are urgently needed to treat OUD. As opioids are effective analgesics and OUD often occurs in conjunction with chronic pain, these novel compounds may be opioids, but they must have a low abuse liability. This could be mediated by diminishing or slowing blood-brain barrier transport, slowing target receptor binding kinetics, and showing a long half-life. NKTR-181 is a PEGylated oxycodol and a MOPr agonist that has slowed blood-brain barrier transport, a long half-life, and diminished likeability in clinical trials. In this study, we examined the signaling and behavioral profile of NKTR-181 in comparison with oxycodone to determine whether further therapeutic development of this compound may be warranted. For this preclinical study, we used a number of in vitro and in vivo assays. The signaling profile of NKTR-181 was determined by the electrophysiological assessment of MOPr-Ca2+ channel inhibition in the nociceptive neurons of rodent dorsal root ganglia. Heterologous cell-based assays were used to assess biased agonism and receptor trafficking. Different rodent behavioral models were used to define the NKTR-181-induced relief of effective and reflexive nociception and drug-seeking behavior as assessed by an intravenous self-administration (IVSA) of NKTR-181. We found that NKTR-181 and oxycodone are partial agonists in G-protein signaling and Ca2+ channel inhibition assays and promote limited MOPr desensitization. However, NKTR-181 inhibits Ca2+ channels by a different mechanism than oxycodone and induces a different pattern of arrestin recruitment. In addition, NKTR-181 has a slower receptor on-rate and a slower rate of Ca2+ channel coupling than oxycodone. This signaling profile is coupled with a slower onset of antinociception and limited drug-seeking behavior in comparison with oxycodone. Together with its known long half-life and slow blood-brain barrier transport, these data suggest that NKTR-181 could be further studied as a pharmacotherapeutic treatment modality for OUD.

Epigenetic Alterations in Prescription Opioid Misuse: New Strategies for Precision Pain Management

Prescription opioids are used for some chronic pain conditions. However, generally, long-term therapy has unwanted side effects which may trigger addiction, overdose, and eventually cause deaths. Opioid addiction and chronic pain conditions have both been associated with evidence of genetic and epigenetic alterations. Despite intense research interest, many questions about the contribution of epigenetic changes to this typology of addiction vulnerability and development remain unanswered. The aim of this review was to summarize the epigenetic modifications detected in specific tissues or brain areas and associated with opioid prescription and misuse in patients who have initiated prescribed opioid management for chronic non-cancer pain. The review considers the effects of opioid exposure on the epigenome in central and peripheral tissues in animal models and human subjects and highlights the mechanisms in which opioid epigenetics may be involved. This will improve our current understanding, provide the basis for targeted, personalized pain management, and thus balance opioid risks and benefits in managing chronic pain.

Novel treatments for chronic pain: moving beyond opioids

It is essential that safe and effective treatment options be available to patients suffering from chronic pain. The emergence of an opioid epidemic has shaped public opinions and created stigmas surrounding the use of opioids for the management of pain. This reality, coupled with high risk of adverse effects from chronic opioid use, has led chronic pain patients and their healthcare providers to utilize nonopioid treatment approaches. In this review, we will explore a number of cellular reorganizations that are associated with the development and progression of chronic pain. We will also discuss the safety and efficacy of opioid and nonopioid treatment options for chronic pain. Finally, we will review the evidence for adenylyl cyclase type 1 (AC1) as a novel target for the treatment of chronic pain.

Pain, the uknown: epistemological issues and related clinical implications

Despite the huge development of pain management in the past decades, pain remains elusive and many patients still remain in the middle of the ford struggling between low drug efficacy and their overuse. A reason for pain elusiveness is its nature of subjective phenomenon, escaping the meshes of the objectivist, mechanist-reductionist net prevailing in medicine. Actually, pain is not only a symptom but an essential aspect of life, consciousness and contact with the world and its noetic and autonoetic components play a key role in the development of the concepts of pleasure-unpleasure and good-evil. The intensity and tolerability of pain and suffering also depends on what the pain means to the patient. The outstanding effects of placebo and nocebo, behavioral and non-pharmacological techniques warrant the need for a shift from the traditional positivist idea of patient as passive carrier of disease to the patient as active player of recovery and move toward a patient's centered approach exploiting individual resources for recovery. Among the mentioned techniques, hypnosis has proved to increase pain threshold up to the level of surgical analgesia, improve acute and chronic pain as well as coping and resilience, helping to decrease both drug overuse and the costs of pharmacological therapy. The wealth of available data suggest the need for a holistic approach, aiming to take care of the individual as an inseparable mind-body unit in its interplay with the environment, where patient's inner world, his/her experience and cognition are taken into due account as powerful resources for recovery through a phenomenological-existential approach.

Risk of Fractures in Older Adults with Chronic Non-cancer Pain Receiving Concurrent Benzodiazepines and Opioids: A Nested Case-Control Study

OBJECTIVE

The aim of this study was to investigate the relationship between the concurrent use of benzodiazepines and opioids and the risk of fractures in older patients with chronic non-cancer pain.

METHODS

Patients with osteoarthritis or low back pain (≥ 65 years of age) included in the Korean National Health Insurance Service-National Sample Cohort database of Korea and with an incident diagnosis of hip, humeral, or forearm fracture between 2011 and 2015 were identified as cases. For each case, four controls were matched for age (within 5 years), sex, and year of cohort entry. We estimated the adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for fractures associated with concurrent use of benzodiazepines and opioids using a conditional logistic regression analysis, adjusting for comorbidities and comedications.

RESULTS

The aOR (95% CI) for the concurrent use of benzodiazepines and opioids was 1.45 (1.22-1.71), compared with those of non-use within 30 days before the index date. The aOR was 1.65 (1.22-2.23) in patients who were continuously receiving benzodiazepines and were newly initiated with concurrent opioids. The aORs for concurrent use were 1.95 (1.39-2.74) and 1.27 (1.03-1.56) in the case of hip fracture and forearm fracture, respectively.

CONCLUSION

The concurrent use of benzodiazepines and opioids was associated with an increased risk of fractures in older patients with chronic non-cancer pain. Therefore, patients continuously receiving benzodiazepines in whom opioids are newly initiated need careful monitoring, and such combined therapy should be limited to the shortest duration possible.

Do acupuncture services reduce subsequent utilization of opioids and surgical interventions compared to noninvasive therapies among patients with pain conditions?

OBJECTIVE

To compare prescribed opioid use and invasive surgical interventions between patients using acupuncture and those using non-steroidal anti-inflammatory drugs (NSAIDs)/Physical Therapy (PT).

DESIGN

Retrospective observational study of administrative claims.

SETTING

Large commercial insurance plan.

SUBJECTS

52,346 each treated with either acupuncture or NSAIDs/PT.

METHODS

Users of acupuncture and NSAIDs/PT were identified from January 1, 2014 to December 31, 2017. The first date of each service was defined as the index date. Acupuncture patients were 1:1 propensity score matched to the NSAIDs/PT group on baseline characteristics. Outcomes included opioid use, subsequent invasive surgical procedures, healthcare utilization such as hospitalizations or emergency department (ED) visits, and costs. These were assessed in the 12-month period before index date (baseline) and 12-month period following index date (follow-up) using difference-in-difference (DID) analysis. Results for opioid use were stratified by those with and without baseline opioid use.

RESULTS

The acupuncture group had fewer patients initiating opioids post-index both among those with (49.2% vs. 56.5%, p < 0.001) and without (15.9% vs. 22.6%, p < 0.001) baseline opioid use. There was a small increase in invasive surgical procedures with acupuncture (3.1% vs. 2.8% p = 0.006). A reduction in ED visits was observed with acupuncture (DID -4.3% for all-cause; -3.3% for pain-related, all p < 0.001). Acupuncture was associated with higher total medical and pharmacy costs (DID +$1,331 per patient, p = 0.006).

CONCLUSIONS

Acupuncture showed a modest effect in reducing opioid use and ED visits. More research on acupuncture's place in emergency care, pain relief, and comparison to other types of non-opioid treatment is needed.

Brain Gene Expression Pattern Correlated with the Differential Brain Activation by Pain and Touch in Humans

Genes involved in pain and touch sensations have been studied extensively, but very few studies have tried to link them with neural activities in the brain. Here, we aimed to identify genes preferentially correlated to painful activation patterns by linking the spatial patterns of gene expression of Allen Human Brain Atlas with the pain-elicited neural responses in the human brain, with a parallel, control analysis for identification of genes preferentially correlated to tactile activation patterns. We identified 1828 genes whose expression patterns preferentially correlated to painful activation patterns and 411 genes whose expression patterns preferentially correlated to tactile activation pattern at the cortical level. In contrast to the enrichment for astrocyte and inhibitory synaptic transmission of genes preferentially correlated to tactile activation, the genes preferentially correlated to painful activation were mainly enriched for neuron and opioid- and addiction-related pathways and showed significant overlap with pain-related genes identified in previous studies. These findings not only provide important evidence for the differential genetic architectures of specific brain activation patterns elicited by painful and tactile stimuli but also validate a new approach to studying pain- and touch-related genes more directly from the perspective of neural responses in the human brain.

Hyporesponsivity to mu-opioid receptor agonism in the Wistar-Kyoto rat model of altered nociceptive responding associated with negative affective state

ABSTRACT

Chronic pain is often comorbid with anxiety and depression, altering the level of perceived pain, which negatively affects therapeutic outcomes. The role of the endogenous mu-opioid receptor (MOP) system in pain-negative affect interactions and the influence of genetic background thereon are poorly understood. The inbred Wistar-Kyoto (WKY) rat, which mimics aspects of anxiety and depression, displays increased sensitivity (hyperalgesia) to noxious stimuli, compared with Sprague-Dawley (SD) rats. Here, we report that WKY rats are hyporesponsive to the antinociceptive effects of systemically administered MOP agonist morphine in the hot plate and formalin tests, compared with SD counterparts. Equivalent plasma morphine levels in the 2 rat strains suggested that these differences in morphine sensitivity were unlikely to be due to strain-related differences in morphine pharmacokinetics. Although MOP expression in the ventrolateral periaqueductal gray (vlPAG) did not differ between WKY and SD rats, the vlPAG was identified as a key locus for the hyporesponsivity to MOP agonism in WKY rats in the formalin test. Moreover, morphine-induced effects on c-Fos (a marker of neuronal activity) in regions downstream of the vlPAG, namely, the rostral ventromedial medulla and lumbar spinal dorsal horn, were blunted in the WKY rats. Together, these findings suggest that a deficit in the MOP-induced recruitment of the descending inhibitory pain pathway may underlie hyperalgesia to noxious inflammatory pain in the WKY rat strain genetically predisposed to negative affect.

Opioid and/or Psychotropic Use Increases Intraprocedural Sedation Drug Requirements

Objectives Acute pain management in opioid users can be challenging in the perioperative period. This study focuses on whether use of opioids increases sedation medication requirements in patients undergoing port placement under moderate sedation.

Materials and Methods A retrospective review was performed on all patients undergoing port placement between June 1, 2017, and June 30, 2019. Exclusion criteria included receiving general anesthesia, no sedation, and errors in data entry. Data collection included demographics, use of opioids, benzodiazepines, antidepressants, tobacco, alcohol, and sedation data.

Results Opioid, benzodiazepine, and selective serotonin reuptake inhibitors (SSRIs)/serotonin-norepinephrine reuptake inhibitors (SNRIs) use was significantly associated with higher sedation drug dose requirements. Patients using opioids required 10.5% higher doses of midazolam compared with nonusers. Benzodiazepine users required 16.3% additional dosage of midazolam than nonusers. Finally, patients on SSRIs/SNRIs medications required 11.8% higher midazolam dosing when compared with nonusers.

Conclusion Anticipating higher needs of sedation medications during procedures in patients with history of psychotropic agents use can allow for more effective sedation and patient satisfaction. More patient and provider awareness is needed on this topic, as health care policy is moving toward value-based healthcare, with patient satisfaction surveys being one of its indicators.

Recent Advances in Peripheral Opioid Receptor Therapeutics

PURPOSE OF REVIEW

Although opioids are excellent analgesics, they are associated with severe short- and long-term side effects that are especially concerning for the treatment of chronic pain. Peripherally acting opioid receptor agonists promise to mitigate the more serious centrally mediated side effects of opioids, and the goal of this paper is to identify and elaborate on recent advances in these peripheral opioid receptor therapeutics.

RECENT FINDINGS

Peripheral opioid receptor agonists are effective analgesics that at the same time circumvent the problem of centrally mediated opioid side effects by (1) preferentially targeting peripheral opioid receptors that are often the source of the pain and (2) their markedly diminished permeability or activity across the blood-brain barrier. Recent novel bottom-up approaches have been notable for the design of therapeutics that are either active only at inflamed tissue, as in the case of fentanyl-derived pH-sensitive opioid ligands, or too bulky or hydrophilic to cross the blood-brain barrier, as in the case of morphine covalently bound to hyperbranched polyglycerols. Recent innovations in peripheral opioid receptor therapeutics of pH-sensitive opioid ligands and limiting opioid permeability across the blood-brain barrier have had promising results in animal models. While this is grounds for optimism that some of these therapeutics will be efficacious in human subjects at a future date, each drug must undergo individualized testing for specific chronic pain syndromes to establish not only the nuances of each drug's therapeutic effect but also a comprehensive safety profile.

Ulinastatin Exhibits Antinociception in Rat Models of Acute Somatic and Visceral Pain Through Inhibiting the Local and Central Inflammation

Introduction

Ulinastatin, a broad-spectrum serine protease inhibitor, has been widely used to treat various diseases clinically. However, so far, the antinociceptive effect of ulinastatin remains less studied experimentally and the underlying mechanisms of ulinastatin for pain relief remain unclear. This study aimed to find evidence of the analgesic effect of ulinastatin on acute somatic and visceral pain.

Methods

The analgesic effect of ulinastatin on acute somatic and visceral pain was evaluated by using formalin and acetic acid-induced writhing test. The analgesic mechanism of ulinastatin was verified by detecting the peripheral inflammatory cell infiltration and spinal glial activation with hematoxylin-eosin (H&E) and immunohistochemistry staining.

Results

We found that both of intraperitoneal (i.p.) pre-administration and post-administration of ulinastatin could reduce the total number of flinching and the licking duration following intraplantar formalin injection in a dose-related manner. However, the inhibitory effect of ulinastatin existed only in the second phase (Phase 2) of formalin-induced spontaneous pain response, with no effect in the first phase (Phase 1). The formalin-induced edema and ulcer were also improved by i.p. administration of ulinastatin. Moreover, i.p. administration of ulinastatin was also able to delay the occurrence of acetic acid-induced writhing and reduced the total number of writhes dose-dependently. We further demonstrated that ulinastatin significantly decreased the local inflammatory cell infiltration in injured paw and peritoneum tissue under formalin and acetic acid test separately. The microglial and astrocytic activation in the spinal dorsal horn induced by intraplantar formalin and i.p. acetic acid injection were also dramatically inhibited by i.p. administration of ulinastatin.

Conclusion

Our results for the first time provided a new line of evidence showing that ulinastatin could attenuate acute somatic and visceral pain by inhibiting the peripheral and spinal inflammatory reaction.

A Critical Review of the Social and Behavioral Contributions to the Overdose Epidemic

More than 750,000 people in the United States died from an overdose between 1999 and 2018; two-thirds of those deaths involved an opioid. In this review, we present trends in opioid overdose rates during this period and discuss how the proliferation of opioid prescribing to treat chronic pain, changes in the heroin and illegally manufactured opioid synthetics markets, and social factors, including deindustrialization and concentrated poverty, contributed to the rise of the overdose epidemic. We also examine how current policies implemented to address the overdose epidemic may have contributed to reducing prescription opioid overdoses but increased overdoses involving illegal opioids. Finally, we identify new directions for research to understand the causes and solutions to this critical public health problem, including research on heterogeneous policy effects across social groups, effective approaches to reduce overdoses of illegal opioids, and the role of social contexts in shaping policy implementation and impact.

Cues conditioned to withdrawal and negative reinforcement: Neglected but key motivational elements driving opioid addiction

Opioid use disorder (OUD) is a debilitating disorder that affects millions of people. Neutral cues can acquire motivational properties when paired with the positive emotional effects of drug intoxication to stimulate relapse. However, much less research has been devoted to cues that become conditioned to the aversive effects of opioid withdrawal. We argue that environmental stimuli promote motivation for opioids when cues are paired with withdrawal (conditioned withdrawal) and generate opioid consumption to terminate conditioned withdrawal (conditioned negative reinforcement). We review evidence that cues associated with pain drive opioid consumption, as patients with chronic pain may misuse opioids to escape physical and emotional pain. We highlight sex differences in withdrawal-induced stress reactivity and withdrawal cue processing and discuss neurocircuitry that may underlie withdrawal cue processing in dependent individuals. These studies highlight the importance of studying cues associated with withdrawal in dependent individuals and point to areas for exploration in OUD research.

Pain Acceptance Creates an Emotional Context That Protects against the Misuse of Prescription Opioids: A Study in a Sample of Patients with Chronic Noncancer Pain

There is solid evidence of an association between several psychological flexibility processes, particularly pain acceptance, and adaptation to chronic pain. However, there are relatively few studies on the relationship between pain acceptance and opioid misuse in chronic pain patients. Thus, the aim of the present study was to test a hypothetical model in which pain acceptance would regulate pain sensations and pain-related thoughts and emotions, which would be related to opioid misuse. The sample comprised 140 chronic pain patients attending two hospitals. All patients were receiving pharmacological treatment, including opioid analgesics. Structural equation modelling analyses showed a significant association between higher pain acceptance and lower pain intensity and catastrophizing, and lower levels of anxiety and depression. Only higher anxiety and depression were significantly associated with increased opioid misuse. The results suggest that levels of anxiety, depression, and pain acceptance must be assessed before opioids are prescribed. Pain acceptance implies a relationship with internal events that protects against anxiety and depression and thus against opioid misuse. Acceptance and Commitment Therapy appears to be particularly appropriate for these patients.

Factors mediating pain-related risk for opioid use disorder

Pain is a complex experience with far-reaching organismal influences ranging from biological factors to those that are psychological and social. Such influences can serve as pain-related risk factors that represent susceptibilities to opioid use disorder. This review evaluates various pain-related risk factors to form a consensus on those that facilitate opioid abuse. Epidemiological findings represent a high degree of co-occurrence between chronic pain and opioid use disorder that is, in part, driven by an increase in the availability of opioid analgesics and the diversion of their use in a non-medical context. Brain imaging studies in individuals with chronic pain that use/abuse opioids suggest abuse-related mechanisms that are rooted within mesocorticolimbic processing. Preclinical studies suggest that pain states have a limited impact on increasing the rewarding effects of opioids. Indeed, many findings indicate a reduction in the rewarding and reinforcing effects of opioids during pain states. An increase in opioid use may be facilitated by an increase in the availability of opioids and a decrease in access to non-opioid reinforcers that require mobility or social interaction. Moreover, chronic pain and substance abuse conditions are known to impair cognitive function, resulting in deficits in attention and decision making that may promote opioid abuse. A better understanding of pain-related risk factors can improve our knowledge in the development of OUD in persons with pain conditions and can help identify appropriate treatment strategies. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'.

Sublingual Buprenorphine/Naloxone and Multi-Modal Management for High-Risk Chronic Pain Patients

Patients with chronic pain managed with opioid medications are at high risk for opioid overuse or misuse. West Virginia University (WVU) established a High-Risk Pain Clinic to use sublingual buprenorphine/naloxone (bup/nal) plus a multimodal approach to help chronic pain patients with history of Substance Use Disorder (SUD) or aberrant drug-related behavior. The objective of this study was to report overall retention rates and indicators of efficacy in pain control from approximately six years of High-Risk Pain Clinic data. A retrospective chart review was conducted for a total of 78 patients who enrolled in the High-Risk Pain Clinic between 2014 and 2020. Data gathered include psychiatric diagnoses, prescribed medications, pain score, buprenorphine/naloxone dosing, time in clinic, and reason for dismissal. A linear mixed effects model was used to assess the pain score from the Defense and Veterans Pain Rating Scale (DVPRS) and daily bup/nal dose across time. The overall retention of the High-Risk Pain Clinic was 41%. The mean pain score demonstrated a significant downward trend across treatment time (p < 0.001), while the opposite trend was seen with buprenorphine dose (p < 0.001). With the benefit of six years of observation, this study supports buprenorphine/naloxone as a safe and efficacious component of comprehensive chronic pain treatment in patients with SUD or high-risk of opioid overuse or misuse.

From pain patient to junkie: An economic theory of painkiller consumption and its impact on wellbeing and longevity

In this paper, I propose a life cycle model of painkiller consumption that combines the theory of health deficit accumulation with the theory of addiction. Chronic pain is conceptualized as a persistent negative shock to lifetime utility that can be treated by pain relief medication. Individuals treated with opioid pain relievers (OPR) develop addiction, which increases their demand for opioids and reduces their welfare and life expectancy through side effects and potential overdose. I calibrate the model for a benchmark American and investigate the comparative dynamics of alternative drug characteristics, pain intensities, and ages of onsets of pain as well as their implications for welfare and life expectancy. Computational experiments are used to identify fully rational and imperfectly rational addiction behavior. Fully rational addicts reduce OPR use when new information about the addictive potential of these drugs arrives. Imperfectly rational addicts further develop their addiction and switch to illicit opioid use. Likewise, a discontinued prescription helps fully rational addicts to quit quickly, while it induces imperfectly rational individuals to take up heroin. I also discuss treatment of OPR addiction and the use of opioids in palliative care.